Alkyl ether organic acid esters are included in drilling and other formation treatment fluids used in hydrocarbon production to provide a demulsifying and defoaming action on foams and emulsions in the producing formation. The action of the compositions is time and temperature dependent and therefore their action can be controlled in situ.
In the production of hydrocarbons from the earth, drilling fluids and formation fracturing fluids are well known and come in many varieties. Where surfactants are included with the fluids, foaming is likely to occur, and frequently surfactants are added to generate foam to assist in removing the particulate products of drilling, or for other purposes. Emulsions may be added deliberately, but also they may be generated due to the pressure and mixing of the fluids with the target hydrocarbons. In most cases it is not desirable for emulsions to be formed in the formation with the hydrocarbons to be produced, since the emulsion will have to be broken after recovery in a separate, time-consuming step. Whether the emulsions are deliberately added or formed in situ, they may migrate under pressure into the pores of the subterranean formation, where they tend to seal the hydrocarbons which are the object of the production process.
A well-controlled method of breaking foams and emulsions in the formation is needed to produce hydrocarbons more efficiently.
We have developed compositions and methods for breaking both emulsions and foams in a subterranean hydrocarbon-bearing formation or a wellbore penetrating such a formation. The method comprises including with a drilling fluid or fracturing fluid (that is, a well treatment fluid) an alkyl ether organic ester of the formula H(CH2)zCOOxe2x80x94[C2H4O]xCyH2Y+1 where z is 0-2, x is 1-5 and y is 4-9, preferably where z is 0-1, x is 2-4, and y is 5-7, and most preferably where z is 0, x is 3, and y is 6xe2x80x94that is, most preferably where the compound is an alkyl ether formate of the formula HCOOxe2x80x94[C2H4O]3C6H7. The formation should have a temperature of at least 100xc2x0 F. At temperatures of 100 degrees F or over, the alkyl ether organic acid ester will hydrolyze to the organic acid and the ethoxylated alkyl alcohol, and act to reduce the foaming tendencies of the surfactants, at least partially by reducing the pH. It will also tend to break emulsions present through the action of the alcohol group on the etherified alkyl. Alternatively, the alkyl ether organic acid ester may be injected into the formation after the fracturing fluid.